How to prepare damaged walls for repainting?

[WreckitRita]

Several years ago, the child painted the toilet walls. 2 days later, the dryer was put on in the adjoining laundry with closed doors, except for the toilet door. No surprises, the paint blistered and that was the end of that joy.  The paint work split as well, with many veins across all the walls. 

Day 1

Enter a lot of life's curveballs across several years... and finally we are here.  I'm scraping walls, discovering the hidden joys of paint scraping and blown plaster with a view to filling, replastering and skimming at a later stage, I assume. 
The map of China wall obviously had moisture trapped between the paint and the plaster and while dry now, it's a clear winner for the disaster awards.

There are four days between first and this second image and it's clearly taking a long time to get through the paint scraping because of the insane adhesion of the paint over the failing plaster.  There was no way to leave the stubborn paint because it had lifted with some of the plaster due to the trapped moisture - become old - and, well - it just has to come off, right?

Day 4

I thought to leave it and seal it (which it seems it had never been before), perhaps try fill the exposed concrete to level out and skim a beaut wall, reseal again and paint.  But I've lost perspective and don't know  where I am, or what I'm doing.
I have Dulux 1 step prep, Gyprock multipurpose joint compound (for some other ceiling work and thought might be good for the skim) - what am I leveling out the blown holes with?
And what am I doing for the rest of the wall(s)?
Am I also looking to waterproof at some point?

The opposite wall with the light switch and other two walls don't have the damage you see on our map of China and surrounding islands.  The paint only seems to go back as far as you can see in the image with the light switch, and attempting to scrape anything else on any of the other walls or areas on the walls either barely scrapes off, or seems to show another colour under the blue paint that we haven't seen before    That colour split can also be seen higher in the middle of our map of China wall (yeah, totally being delirious and stupid to get myself through the trauma of it all.  It's a hard, hot mess and so am I.)

Any product and procedural advice would be really appreciated.
Thanks kindly,
A 60 year old woman with sore hands  

[Jeanagh]

🤣 that's how we learn hun, trial and error. At least we can give it a go. Be proud of what we can achieve; especially between bunnings and YouTube

[WreckitRita]

😀 exactly right.  Happy days, @Jeanagh   🎶